A survey by ICM found that 41% of pre-adolescents felt lonely. Photograph: Christopher Thomond

The lives of Britain's children are being blighted by problems of loneliness and low self-esteem during the vulnerable middle years of youth between six and 13, research for the charity Action for Children revealed today.

It said paediatricians have established that a child's emotional wellbeing at age 10 determines mental health at 16 and life chances at 30.

But most parents and politicians are giving priority to early years education and the problems of older teenagers, without paying due regard to the needs of children in the middle years.

The charity interviewed 165 vulnerable pre-adolescents who use its support services, to identify the type of emotional problems they experience. It found 53% had difficulty controlling their temper, 35% were bullied and 25% felt lonely.

It then commissioned ICM to survey more than 2,000 parents and adults to establish whether these problems are commonplace in British families. The poll found 52% said children of this age had problems controlling their temper, 66% thought they encountered bullying and 41% experienced loneliness.

In a report entitled Stuck in the middle: the importance of supporting six to 13-year-olds, the charity said: "Between these ages, children are going through a succession of important transformations. They are becoming more independent, spending less time with parents, physical changes are happening, relationships are developing and they are spending more time with friends and peers. They become more self-aware...

"This is the age at which they may have their first real exposure to bullying and to damaging or dangerous peer group pressure. For the first time they may find themselves exposed to smoking, drug or alcohol use, juvenile crime, or risky sexual activity. They are also targeted as never before by the commercial world through overt advertising and editorial."

The report added: "Often the line between advertising and entertainment is intentionally blurred, with companies such as Haribo and McDonald's hosting games on their websites to attract children. Companies are spending millions to make children brand aware ... Early and deep immersion into consumerism is associated with depression, anxiety and general dissatisfaction, and studies suggest vulnerable children are more exposed than most."

Children might also be disturbed by the loss of a supportive primary teacher on moving to secondary school, parental separation or poverty. Adolescent aggression could often be traced back to negative experiences in the middle years.

Clare Tickell, the chief executive, said: "It's a major concern that children themselves are identifying these serious problems. As a society we understand what pre-schoolers and teenagers need, but six to 13-year-olds are being overlooked and these ages are crucial.

"At this age children need to be children, they need to be listened to and their self-esteem and confidence built. If not, it could lead to darker days for them as adults. Children, and especially the most vulnerable children, don't have to be caught in this trap."

Claire Tyler, chief executive of Relate, said: "The quality of family and peer relationships are paramount to the happiness of children, as this report shows. The relationships that children experience at this stage in life will often form the template for how future relationships are conducted. Parents and schools can do a lot to improve a child's quality of life both in the home and through specialist services."

The charities called for cross-party agreement on the support that all children and young people need from birth to 21. They said: "All children need at least one trusted adult who is there for them as long as it takes, especially at times of transition."

The Department for Children, Schools and Families said a survey in 2007 of 110,000 pupils aged 10-15 found 93% said they felt happy about life.

A spokeswoman added: "We are absolutely committed to improving the wellbeing of all children and young people, whatever their age ... We know that outdoor play has many benefits to children, and parents tell us that it is key to a happy and enjoyable childhood. We have committed £225m in funding for play." She said this would create 30 new adventure playgrounds or play parks for eight to 13-year-olds. Another 3,500 play areas nationally would be be rebuilt or renewed.